13 Jun 2026

Optics Standard Problems

Standard competitive exam problems in optics with answer key.

optics gate-2024 csir-net-2023 jest-2022

These are original standard problems based on frequently tested competitive-exam patterns.

Q: In Young's double slit experiment, fringe width is
A: $\lambda D/d$
B: $dD/\lambda$
C: $\lambda d/D$
D: $D/(\lambda d)$
ANSWER: A
SOURCE: GATE 2024 style
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Q: Brewster's law is
A: $\tan\theta_B=n_2/n_1$
B: $\sin\theta_B=n_2/n_1$
C: $\cos\theta_B=n_1/n_2$
D: $\theta_B=0$
ANSWER: A
SOURCE: CSIR-NET 2023 style
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Q: The Rayleigh criterion for a circular aperture gives angular resolution approximately
A: $1.22\lambda/D$
B: $D/\lambda$
C: $\lambda/2D^2$
D: $2D/\lambda$
ANSWER: A
SOURCE: JEST 2022 style
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Q: A half-wave plate introduces phase retardation
A: $\pi/2$
B: $\pi$
C: $2\pi$
D: $0$
ANSWER: B
SOURCE: GATE 2021 style
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Q: For single-slit diffraction, the first minimum satisfies
A: $a\sin\theta=\lambda$
B: $a\cos\theta=\lambda$
C: $d\sin\theta=\lambda/2$
D: $a=\lambda\sin^2\theta$
ANSWER: A
SOURCE: CSIR-NET 2020 style
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Q: In a Michelson interferometer, moving one mirror by distance $d$ changes optical path by
A: $d$
B: $2d$
C: $d/2$
D: $0$
ANSWER: B
SOURCE: GATE style
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Q: Malus law for transmitted intensity through an analyzer is
A: $I=I_0\cos^2\theta$
B: $I=I_0\sin\theta$
C: $I=I_0\tan\theta$
D: $I=I_0/\cos^2\theta$
ANSWER: A
SOURCE: CSIR-NET style
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Q: The resolving power of a grating increases with
A: number of illuminated slits
B: decreasing all wavelengths to zero only
C: removing interference
D: reducing grating order to zero
ANSWER: A
SOURCE: JEST style

Problem Sheet Standard MCQs